In certain processing systems, a workpiece is disposed in a process chamber, which is maintained at vacuum conditions. The workpiece may also be disposed on a movable shaft in the process chamber that allows the workpiece to be moved relative to the incoming ion beam.
In these systems, the movable shaft passes through an opening in a wall in the process chamber such that part of the shaft is disposed outside the process chamber, while a second part of the shaft is within the process chamber. An air bearing may be used to provide near frictionless motion between the shaft and the wall. The air bearing also serves to maintain the pressure difference between the process chamber and the outside environment. The shaft is able to be translated so that the portion of the shaft that is disposed within the process chamber can be increased or reduced.
Contaminants, such as water vapor, may collect on the portion of the shaft that is disposed outside the process chamber. As the shaft is translated relative to the wall of the process chamber, these contaminants may enter the process chamber through the air bearing. Once inside the process chamber, these contaminants can affect the yield of the workpieces, or may negatively affect the components within the process chamber.
Therefore, it would be beneficial if there were a system that allowed a shaft to be moved relative to the wall of a process chamber, while reducing or minimizing the amount of contaminants that are introduced into the process chamber as the shaft extends into the chamber.